Mary E. Kerr

The effects of admission alcohol level on cerebral blood flow and outcomes after severe traumatic brain injury

This study examined the relationship between admission serum alcohol level (ETOH) and cerebral blood flow (CBF) and outcomes in the adult traumatic brain injured (TBI) population. We hypothesized that individuals with ETOH > 100 mg/dL will have decreased blood flow on admission and poorer outcomes. Eighty subjects, age 16-65, with severe TBI (Glasgow Coma Score [GCS] </= 8) were entered into the study. Correlational analysis assessed the relationship between ETOH and admission severity of injury scores as measured by Marshall and APACHE III scores, CBF, and outcomes. Comparison of CBF and outcomes between groups based on admission serum ETOH level was conducted with analysis of variance and post hoc Scheffé analyses as well as regression analysis. There was a significant relationship between serum ETOH level and GCS (p = 0.02), but not APACHE III scores (p = 0.12) or Marshall scores (p = 0.27). There was a significant correlation between global CBF and serum ETOH level (p = 0.02). There was no statistically significant association between serum ETOH level and GOS at 3 (p = 0.97), 6 (p= 0.56), or 12 (p = 0.73) months after injury. The data indicated that serum ETOH levels > 100 mg/dL at the time of admission after a TBI were associated with a decrease in global CBF. Elevated serum ETOH level at time of injury did not, however, impact outcomes.

Relationship between arterial carbon dioxide and end-tidal carbon dioxide in mechanically ventilated adults with severe head trauma.

OBJECTIVE To examine the agreement and association of a noninvasive method of measuring CO2 (using end-tidal PCO2) with PaCO2 in mechanically ventilated adults with severe head trauma. DESIGN A prospective, quasi-experimental, repeated-measures study was used to compare end-tidal PCO2 and PaCO2 at two time points: before and after a standardized endotracheal suctioning procedure. INTERVENTIONS Controlled intervention of endotracheal suctioning. SETTING The study was conducted at two intensive care units designated as Level 1 trauma centers. PATIENTS A consecutive sample of 35 severe head-injured patients with a Glasgow Coma Scale score of < or = 8. MEASUREMENTS AND MAIN RESULTS End-tidal PCO2 and PaC02 values were simultaneously obtained and compared. End-tidal PCO2 was measured, using a sidestream sensor placed in line of the ventilator circuits deadspace. Arterial gases were drawn from an indwelling arterial catheter. No relationship was found between arterial and end-tidal measures (range r2 = .09 to r2 = .11). Using the Bland-Altman technique, agreement decreased as the amount of positive end-expiratory pressure increased. When a subset of patients (mechanically ventilated, with positive end-expiratory pressures of < 5 cm H2O, paralyzed, and sedated) were examined (n = 12), the correlation between the CO2 measures improved (r2 = .77). CONCLUSIONS This study indicated that end-tidal PCO2 monitoring correlated well with PaCO2 in patients without respiratory complications or without spontaneous breathing, resulting in rebreathing of gases. However, its clinical validity is questionable in patients who have the greatest need for end-tidal PCO2 monitoring (i.e., patients who have respiratory distress or who are breathing spontaneously and overriding the ventilator.

Factors that contribute to complications during intrahospital transport of the critically ill.

Transporting patients from the protective environment of the intensive care (ICU) unit to other areas of the hospital has become increasingly common since high technologic testing has become an integral part of health care assessment. The hazards of moving critically ill patients by ambulance or air transport are well recognized and standards of care have been developed based on delineation of these risks. Despite the existing evidence of hazards of interhospital hospital transport, less attention has been given to the potential hazards associated with the intrahospital transport of critically ill patients. A high incidence of serious hemodynamic or respiratory alteration is associated with the intrahospital transport of critically ill patients. In one third of critically ill intrahospital transports, technical mishaps (eg, i.v. disconnects, which could potentially lead to deleterious physiologic outcomes) may occur. As patient acuity increases, there is a greater risk of hemodynamic instability. The purpose of this study was to further investigate the patient complications during transportation to and from the ICU to a diagnostic or treatment site. The sample consisted of thirty-five critically ill patients from the Neuro/Trauma ICU who required continuous physiological monitoring and had an arterial catheter in place. The systemic blood pressure, heart rate and peripheral oxygen saturation were monitored at nine time points throughout the transport process. The incidence of defined technical mishaps that occurred when the patient was off the unit were also recorded. Transport factors examined included the length of time spent off the unit and the number and level of personnel accompanying the patient. A within-subject repeat measure design was used to examine the physiologic changes and mishaps that occurred. Results indicate that while the majority of patients experienced some physiologic responses as a result of transport, the responses were not of sufficient magnitude to be classified as a deleterious. Twenty-three technical mishaps, which included inadvertent ventilator and electrocardiogram disconnects, power failures, interruption of medication administration and disconnection of drainage devices were observed. Factors related to these occurrences of technical mishaps were the number of intravenous solutions and infusion pumps and the time spent outside of the ICU environment.

The impact of cardiac complications on outcome in the SAH population

Objectives –  To determine the impact of cardiac complications (CdCs) on outcomes in patients with acute subarachnoid hemorrhage (SAH).

Identification and quantification of the hydroxyeicosatetraenoic acids, 20-HETE and 12-HETE, in the cerebrospinal fluid after subarachnoid hemorrhage.

PURPOSE The monohydroxylated metabolite of arachidonic acid, 20-hydroxyeicosatetraenoic acid (20-HETE), is a potent vasoconstrictor of cerebral microvessels. 20-HETE formation is substantially elevated in the cerebral spinal fluid (CSF) in the rat subarachnoid hemorrhage (SAH) model. The presence of 20-HETE in human CSF has not been demonstrated. Therefore, it was the purpose of this study to determine if HETE metabolites are present in human CSF after SAH. METHODS CSF samples were collected daily from four SAH patients over 15 days. HETE metabolites were separated by HPLC with identification by ion-trap MS/MS and quantification via single quadrupole MS operating in negative single ion monitoring mode. RESULTS Two major metabolites were identified as 12-HETE and 20-HETE. 20-HETE maximal concentrations were 2.9 and 0.7 ng/ml at approximately 70 h in the two patients with symptomatic cerebral vasospasm (SV) after SAH. Concentrations of 12-HETE in these patients peaked at 21.9 ng/ml and 2.8 ng/ml. Concentrations of 20-HETE and 12-HETE were non-detectible in the majority of the samples obtained from two matched SAH patients without SV. CONCLUSIONS This study is the first to demonstrate that 20-HETE and 12-HETE are present in the CSF of SAH patients at physiologically relevant concentrations. Based on this information future prospective studies will allow for the delineation of the role of these metabolites in the pathogenesis of SAH.

Traumatic brain injury research: a review of clinical studies.

There is a growing volume of research on trauma brain injury (TBI) as evidenced by a recent Medline search that reported over 6000 articles published on TBI in the past 5 years.

NIH Roundtable on Emergency Trauma Research

STUDY OBJECTIVE The National Institutes of Health (NIH) formed an NIH Task Force on Research in Emergency Medicine to enhance NIH support for emergency care research. The NIH Trauma Research Roundtable was convened on June 22 to 23, 2009. The objectives of the roundtable are to identify key research questions essential to advancing the scientific underpinnings of emergency trauma care and to discuss the barriers and best means to advance research by exploring the role of trauma research networks and collaboration between NIH and the emergency trauma care community. METHODS Before the roundtable, the emergency care domains to be discussed were selected and experts in each of the fields were invited to participate in the roundtable. Domain experts were asked to identify research priorities and challenges and separate them into mechanistic, translational, and clinical categories. During and after the conference, the lists were circulated among the participants and revised to reach a consensus. RESULTS Emergency trauma care research is characterized by focus on the timing, sequence, and time sensitivity of disease processes and treatment effects. Rapidly identifying the phenotype of patients on the time spectrum of acuity and severity after injury and the mechanistic reasons for heterogeneity in outcome are important challenges in emergency trauma research. Other research priorities include the need to elucidate the timing, sequence, and duration of causal molecular and cellular events involved in time-critical injuries, and the development of treatments capable of halting or reversing them; the need for novel experimental models of acute injury; the need to assess the effect of development and aging on the postinjury response; and the need to understand why there are regional differences in outcomes after injury. Important barriers to emergency care research include a limited number of trained investigators and experienced mentors, limited research infrastructure and support, and regulatory hurdles. CONCLUSION The science of emergency trauma care may be advanced by facilitating the following: (1) development of an acute injury template for clinical research; (2) developing emergency trauma clinical research networks; (3) integrating emergency trauma research into Clinical and Translational Science Awards; (4) developing emergency care-specific initiatives within the existing structure of NIH institutes and centers; (5) involving acute trauma and emergency specialists in grant review and research advisory processes; (6) supporting learn-phase or small, clinical trials; (7) performing research to address ethical and regulatory issues; and (8) training emergency care investigators with research training programs.

EFFECT OF SHORT-DURATION HYPERVENTILATION DURING ENDOTRACHEAL SUCTIONING ON INTRACRANIAL PRESSURE IN SEVERE HEAD-INJURED ADULTS

A repeated measures randomized within-group design was used to determine the effectiveness of controlled short-duration hyperventilation (HV) in blunting the increase of intracranial pressure (ICP) during endotracheal suctioning (ETS). A multimodal continuous real-time computerized data acquisition procedure was used to compare the effects of two HV ETS protocols on ICP, arterial pressure, cerebral perfusion pressure (CPP), heart rate, and arterial oxygen saturation in severe head-injured adult patients. The results indicated that short-duration HV for 1 minute, which decreases the PaCO2, reduced ETS-induced elevations in ICP while maintaining CPP. However, it is not clear whether short-duration HV is neuroprotective, particularly in ischemic regions of the brain. Therefore, before a change in practice is implemented on the use of short-duration HV as a prophylactic treatment against ETS-induced elevations in ICP, additional questions on cerebral oxygen delivery and uptake need to be answered.

Relationship between apoE4 allele and excitatory amino acid levels after traumatic brain injury.

ObjectiveApolipoprotein E isoform (E4) has been posited to affect outcomes after central nervous system injury. This project sought to determine the relationship between the apoE4 allele and the recovery of amino acid neurotransmitters (aspartate, glutamate, and lactate/pyruvate ratio [L/P]) following a traumatic brain injury (TBI) after controlling for patient characteristics. DesignThis prospective clinical study examined neurotransmitters and L/P within the cerebrospinal fluid and compared the trends by apoE genotypes. SettingAdults with TBI were recruited from a neurotrauma intensive care unit within a trauma I university medical center. PatientsNinety-one patients were enrolled into the study after a severe TBI (Glasgow Coma Scale [GCS] score, ≤8). Cerebrospinal fluid was serially sampled from a ventriculostomy every 4 hrs for the first 24 hrs and every 6 hrs for 25–120 hrs after injury. Measurements and Main ResultsHierarchical linear modeling analyses were used to compare the change of glutamate, aspartate, and L/P over time by the presence or absence of the apoE4 allele, with GCS score, sex, race, and therapeutic hypothermias included as covariates. There was a significant apoE4 allele group effect on both the linear and quadratic slopes in aspartate. In glutamate, the rate of change in glutamate was statistically related to GCS score. There was no significant difference in the glutamate response over time by the presence of the apoE4 allele. There was a significant difference in the change in L/P across time, with faster recovery when the apoE4 allele was absent. ConclusionsRecovery of aspartate and L/P differed depending on the presence of the apoE4 allele. Patients with the allele had significant increased and sustained levels of aspartate and L/P after TBI. Changes in glutamate were related to severity of illness and were independent of the presence of the apoE4 allele.

Cerebrospinal fluid ferritin level, a sensitive diagnostic test in late-presenting subarachnoid hemorrhage.

The workup of patients with suspected subarachnoid hemorrhage (SAH) presenting late is complicated by a loss of diagnostic sensitivity of computed tomography (CT) brain imaging and cerebrospinal fluid (CSF) bilirubin levels. In this prospective longitudinal study of CSF ferritin levels in SAH, serial CSF samples from 14 patients with aneurysmal SAH requiring extraventricular drainage (EVD) were collected. The control group comprised 44 patients presenting with headache suspicious of SAH. Nine patients underwent a traumatic spinal tap. CSF ferritin levels were significantly higher in the patients with SAH compared with controls (P < .0001). The upper reference range of CSF ferritin is 12 ng/mL, and there was no significant difference between the traumatic and normal spinal taps (mean, 9.0 ng/mL vs 3.9 ng/mL; P = .59). CSF ferritin levels increased after SAH, from an average of 65 ng/mL on day 1 to 1750 ng/mL on day 11 (P < .01). Both the Fisher and Columbia CT scores were significantly correlated with CSF ferritin level. The increase in CSF ferritin level after SAH and possibly may provide additional diagnostic information in patients with suspected SAH who present late to the clinic.